The present invention relates to an apparatus for measuring the moisture vapor transmission rate of a shoe.
The systems currently used to measure the moisture vapor transmission rate of items of clothing or shoes relate exclusively to the materials that compose them.
They allow to obtain data related to the moisture vapor transmission rate, defined in milligrams per square centimeter per hour or in grams per square centimeter per day.
The basic conditions of the tests are defined, for example, in the UNI 8429 standard, but they cannot be applied for example to an entire shoe, since they do not include the necessary conditions, such as the presence of multiple layers, foot movement and the different perspiration production conditions.
A complex simulation system has also been devised which is based on measuring the difference in moisture vapor transmission rate between a water-resistant but not vapor-permeable item and an item provided with a waterproof and vapor-permeable membrane.
This system is described for example in U.S. Pat. No. 4,918,981, which indeed relates to a method and an apparatus for testing items of apparel to be worn, such as for example shoes, gloves, et cetera which define closed elements, for the transmission of the vapor produced by perspiration.
The apparatus comprises a thin, flexible and waterproof closed liner which is highly vapor-permeable, is inserted in the item to be tested and is filled with water.
The water can be heated in order to simulate the temperature of the body and produce a high concentration of moist vapor inside the item.
The amount of moisture transferred to the environment outside the tested item as well as the amount of moisture absorbed and condensed in said item can be measured by virtue of weight differences on measurements performed before, during and after the test period.
The application of this system to shoes, however, does not yield uniform and convincing results, because the actual operating conditions to which the foot is subjected, particularly during walking and/or running, are not simulated, and because the microclimate that is produced inside a shoe dunng use is not reproduced.
The aim of the present invention is to provide an apparatus for measuring the moisture vapor transmission rate of a shoe which is capable of evaluating the amount of vapor evaporated toward the outside, the amount of vapor absorbed by the components of the shoe and the amount of moisture in contact with the foot absorbed by the inner sole, all this in dynamic conditions which simulate the movement of the foot.
Within the scope of this aim, a consequent primary object is to provide an apparatus which can measure the moisture vapor transmission rate of the sole, of the type described in EP- 382904, fitted on a shoe.
A further object is to provide in apparatus which is capable of simulating as accurately as possible the human foot and the microclimate that is produced inside a shoe.
Another object is to provide an apparatus which is structurally simple and easy to use.
This aim, these objects and others which will become apparent hereinafter are achieved by an apparatus for measuring the moisture vapor transmission rate of a shoe according to the present invention, characterized in that it comprises, on a supporting footing:
a hollow body made of self-supporting material, which reproduces the shape of a foot and is designed to support the shoe to be tested, said body having through holes which are distributed thereon and containing water;
a sock made of waterproof and vapor-permeable material, arranged so as to enclose said hollow body;
a presser for performing relative movements with said hollow body between a configuration in which it is spaced from and a configuration in which it is compressed against the sole of the shoe;
means for heating the water in said hollow body to a preset and constant temperature.
Advantageously, means are provided for measuring the weight of said hollow body with all the items associated therewith and the shoe to be tested.
Conveniently, sensors are arranged in the shoe to be tested in order to evaluate the relative humidity in different points of the foot.